Spending most of her time on boats, sailing the oceans from Antarctica to the Arctic, Claire Evans is not your typical virologist. Catherine Brahic caught up with her on board the Amundsen icebreaker in the Canadian Arctic and heard about her mission&colon; to uncover the role that viruses play in regulating the ecology of the polar seas.

Advertisement

Marine viruses do not cause human diseases. So why are you are interested in them?

If I took a teaspoon of seawater, depending on where I was, there would be something like 4 to 16 million viruses in there. They probably infect everything from very basic cells like phytoplankton, right up to whales and polar bears.

I’m particularly interested in the viruses that infect phytoplankton and bacteria, the guys at the bottom of the food chain. We really want to find out how they are killed and what happens to the matter and energy they contain.

Do the viruses have a big effect, ecologically?

Viral replication – the lytic cycle – essentially short-circuits the food web. Viruses infect phytoplankton, burst their cells open and release the contents to the water column.

They prevent matter and energy, in the form of carbon, being passed up to the top predators. As much as 25% of all the photosynthetically fixed carbon in the oceans may be shunted back to the bottom of the food web like this every day.

Could they affect us?

Some of my most recent research shows that when phytoplankton are infected by viruses, they produce less polyunsaturated fatty acids. These are important in the food web for things like egg development and growth. They affect the health of the overall food web, and humans benefit from them too – these are the omega fatty acids that we are essential in our diet.

You are looking for viruses at the poles, which are changing very rapidly because of climate change. Do you think the role of viruses here will also shift?

We know very little about viruses in the polar regions. We need to understand how things stand now in order to understand how they might change.

Ecologists say that species from the lower latitudes will move into the higher latitudes – will they bring their own viruses with them? How will that change the flow of energy at the poles? It could change the structure of the entire ecosystem.

We know that if a cell is killed by a virus it yields far, far less dimethylsulphide. So if algal blooms that are normally grazed by zooplankton are suddenly infected by viruses, you could get fewer clouds.

DMS is also the main non-human source of acid rain. And it doesn’t just affect how many clouds there are, but also the type of clouds that form and how much these clouds reflect the sun’s rays back out into space.

So viruses could potentially change the weather at the poles?

In theory, yes. The more I study these systems the more I believe the biological systems and the physical ones are interlinked. If you push one part it will impact on the whole.

What do you hope to see in the Arctic springtime?

When the ice really starts to melt the phytoplankton will start to bloom and the food chain will get a large influx of carbon. I think this is when we might see viruses becoming active.

What are some of the difficulties of working on a boat stuck in the polar regions?

It seems silly to say this, but the cold can be a real problem. In Antarctica, I put the water samples I was studying in incubators on the ship’s deck. I wanted them to be as close to the natural conditions as possible.

The incubators froze, the samples froze. There was no way I could use them. I couldn’t defrost the incubators until I got out of the really cold regions in the Weddell Sea.

Claire Evans is a researcher at the Royal Netherlands Institute for Sea Research